The present invention relates to a metal static gasket forming an annular body about an axis ZZxe2x80x2.
The invention relates more particularly to gaskets for providing sealing under very difficult conditions of use. Such gaskets can withstand temperatures that are very high or very low, and fluid pressures that are extreme, and they can also withstand large mechanical forces.
High performance static gaskets used in such environments are already known, in particular from documents FR 2 726 879 and FR 2 757 923.
Gaskets of that type all rely on the same principle: deformation of a channel-section profile.
FIG. 5 shows an example of a prior art channel-section gasket 40. The gasket 40 comprises an annular body 47 about an axis ZZxe2x80x2, which body is extended laterally by lips 42 and 43 which are themselves associated with end portions 44 and 45 that define the contact surfaces of the gasket 10. Sealing is achieved by compressing the end portions 44, 45 between two flanges (not shown). Profiles of that type have been developed to present a large amount of usable restitution (where usable restitution is the maximum axially-symmetrical opening between the bearing faces of the housing for the gasket that the gasket can accommodate without leaking) for a small size of profile. Although such gaskets present characteristics that are satisfactory concerning performance and lifetime, they are nevertheless relatively difficult to manufacture because of the problems encountered when machining (turning) profiles of very small dimensions.
Very tight manufacturing tolerances contribute to make such gaskets relatively expensive.
The invention seeks to remedy the above-mentioned drawbacks and to provide a gasket which presents manufacturing tolerances that are less tight than those in the prior art so as to enable such a gasket to be made using xe2x80x9cmass productionxe2x80x9d techniques.
The invention seeks to provide a static gasket which presents usable restitution that is equivalent to or greater than that of channel-section static gaskets for a profile of the same size.
The invention also seeks to provide a static gasket which presents excellent qualities in terms of mechanical strength, materials compatibility with the fluids and the surrounding materials, and tolerance to severe conditions of use such as vast temperature or pressure ranges.
These objects are achieved by a metal static gasket forming an annular body about an axis ZZxe2x80x2, the profile of the gasket in axial half-section being an elongated S-shape and comprising a lateral first portion which defines the inner peripheral surface of the gasket, a lateral second portion which defines the outer peripheral surface of the gasket, said lateral first and second portions being offset from each other in the axial direction of the gasket, and curved third and fourth portions of undulating shape, wherein the curved third portion of undulating shape has, at one of its ends, a first contact region that is substantially rectilinear and extends perpendicularly to the axis of the gasket and that is connected to one of the ends of the lateral second portion, and wherein the curved fourth portion of undulating shape has, at one of its ends, a second contact region that is substantially rectilinear and extends perpendicularly to the axis of the gasket, and that is connected to one of the ends of the lateral first portion.
The invention thus provides a metal static gasket of design that is simpler than that of the gaskets that have been developed in the prior art, but which presents sealing performance that is equivalent or better. In particular, the shape of the profile of the gasket of the invention presents dimensional characteristics that are adapted to the presently-existing housings for receiving gaskets of larger profile. With smaller profile, the gasket of the invention presents usable restitution that is equivalent to that of gaskets having a channel-section profile, and they do so at smaller axial compression force. This potentially improves the tightening of the connections between which the gasket is placed without it being necessary to exert any radial force on the gasket.
The shape of the profile of the gasket of the invention ensures that contact with and pressure on the sealing tracks provides high performance, capable of satisfying the severe requirements expected of gaskets of very small dimensions.
According to a feature of the present invention, the lateral first and second portions are rectilinear and extend parallel to the axis of the gasket.
In an embodiment, the third and fourth portions of undulating shape are upwardly sloping from the inside circumference towards the outside circumference of the gasket.
In another embodiment, the third and fourth portions of undulating shape are downwardly sloping from the inside circumference towards the outside circumference of the gasket.
More particularly, the gasket of the invention may be constituted by a metal substrate of thickness lying in the range 1.4 mm to 1.6 mm.
In a particular embodiment, its height without any coating lies in the range 2.45 mm to 2.65 mm.
Advantageously, the gasket of the invention is coated in a layer of silver of thickness less than or equal to 0.04 mm.
In particular, the gasket of the invention may be made to have small dimensions, for example an inside diameter of about 16.5 mm and an outside diameter of about 21 mm.
According to another particular characteristic, the gasket can be constituted by an Inconel substrate.
The invention also provides a method of manufacturing a metal static gasket, the method comprising the steps of: cutting out an annular body from a sheet of metal or alloy; holding an outer peripheral portion of the annular body in a press constituted by a punch, a die, and a clamp, the outer portion being held between the die and the clamp in a plane extending perpendicularly to the axis of the ring; and causing the punch to advance against an inner peripheral portion of the annular body in such a manner that said annular body, when deformed in this way, presents an elongated S-shape in axial half-section.
The invention thus provides a xe2x80x9cgentle embossingxe2x80x9d method of manufacture which considerably simplifies manufacture of the gasket while retaining the required performance for the gasket. The method of manufacture of the invention thus considerably improves the reliability of gaskets manufactured using this method. The difficult operations of turning very small gaskets are avoided, thereby reducing risks during manufacture. The small bending angles due to the gentle embossing make it possible to conserve good mechanical strength and considerable usable restitution for the gasket. The manufacturing method of the invention also makes it possible to use xe2x80x9cmass productionxe2x80x9d production techniques.
According to a particular characteristic, the method further comprises a step consisting in covering said annular body in a coating material.
Advantageously, the coating material is constituted by a layer of silver having a maximum thickness of 0.04 mm.
According to another particular characteristic, said metal or alloy sheet is constituted by Inconel having a thickness lying in the range 0.6 mm to 5 mm.
The method of manufacture of the invention is compatible in general with all types of metal and alloy for which the breaking elongation of the material is greater than 30%.